To reduce the quantity of NOx and particulate matter emitted to the atmosphere during internal combustion engine operation, a number of exhaust aftertreatment devices have been developed. A need for exhaust aftertreatment systems particularly arises when diesel combustion processes are implemented. Typical aftertreatment systems for diesel engine exhaust may include one or more of a diesel particulate filter (DPF), a selective catalytic reduction (SCR) system, a hydrocarbon (HC) injector, and a diesel oxidation catalyst (DOC).
During engine operation, the DPF traps soot emitted by the engine and reduces the emission of particulate matter (PM). Over time, the DPF becomes loaded and begins to clog. Periodically, regeneration or oxidation of the trapped soot in the DPF is required for proper operation. To regenerate the DPF, relatively high exhaust temperatures in combination with an ample amount of oxygen in the exhaust stream are needed to oxidize the soot trapped in the filter.
The DOC is typically used to generate heat useful for regenerating the soot loaded DPF. When hydrocarbons (HC) are sprayed over the DOC at or above a specific light-off temperature, the HC will oxidize. This reaction is highly exothermic and the exhaust gases are heated during light-off. The heated exhaust gases are used to regenerate the DPF.
Over time, however, the DPF may degrade and become less effective. Replacement of the DPF or another exhaust treatment device may be necessary. Alternatively, the exhaust treatment device may be serviced or otherwise rejuvenated when the exhaust treatment device is removed from the system.
DPFs, DOCs and the like have been coupled to relatively small displacement internal combustion engines for automotive use. It may also be desirable to treat the exhaust emitted from engines in other applications including diesel locomotives, stationary power plants and marine vessels. These systems may be equipped with relatively large diesel compression engines. The exhaust mass flow rate from the larger engines may be more than ten times the maximum flow rate typically provided. The size and weight of the exhaust treatment devices required for large engines may make the components unwieldy and very costly. Therefore, a need may exist in the art for an arrangement to easily service and support the devices for treating the exhaust output from a large diesel engine. Some of the exhaust treatment devices such as DPFs are relatively fragile and susceptible to fracture. Care should be taken during DPF replacement and operation to avoid impact loading. Furthermore, it may be desirable to maintain a predetermined exhaust flow direction through the exhaust treatment device and also a predetermined rotational alignment between exhaust treatment devices.